A steering wheel is a type of steering control for a vehicle that is rotated by a driver to provide steering inputs into the vehicle. Simply stated, by rotating the steering wheel to the left or right, the vehicle may be steered to the left or right, respectively. Steering wheels are generally circular having an outer ring that may be grasped by the driver's hand connected to a center hub by one or more spokes. The hub of the steering wheel may be connected to a steering-wheel shaft that runs down into a steering column, and into, under, or behind an instrument panel. In automobiles, the steering-wheel shaft is typically connected to the wheels of the vehicle through a steering system. A steering system may have a gearbox to transfer movement and energy from one device to another. The gearbox may also be used to increase torque by allowing for the steering wheel to be rotated numerous revolutions while only turning the wheels a portion of a revolution.
A rack-and-pinion gearbox and a recirculating-ball gearbox are commonly used to provide a direct mechanical link between the steering wheel and the steerable vehicle wheels. However, some steer-by-wire systems that do not require direct mechanical contact have been developed. Steer-by-wire systems measure the rotational input of the steering wheel and use actuators to turn the steerable wheels of the vehicle. Steer-by-wire systems may work in combination with a gearbox, or may replace the gearbox all together and use the actuators to provide the torque needed to turn the vehicle wheels. Most modern steering systems, whether they are a traditional steering system or a steer-by-wire system, typically employ actuators to provide power assisted steering to aid in the turning of the wheels requiring less input effort at the steering wheel.
In addition to its use in steering, the steering wheel may provide a location for numerous other vehicle controls. The steering wheel has long been the usual location for a button to activate an automobile's horn. Modern automobiles may also have other controls, such as cruise control, audio system and telephone controls, and paddle shifters built into the steering wheel to minimize the extent to which the driver must take their hands off the wheel (and eyes off the road) while driving. The hub of the steering wheel is also commonly used as a location for a driver side airbag. The addition of the airbag, shifters, controls and buttons has decreased visibility of other vehicle components located behind and under the steering wheel.
Some vehicles use an ignition switch or lock to start the vehicle. The ignition switch may be a button that the driver presses to start the vehicle. The ignition lock may be used with a key, in which the key is inserted into the ignition lock to start the vehicle. Ignition switches and locks may be located on the steering column or on the instrument panel near the base of the steering column. The steering wheel may make it difficult for the driver to see the ignition switch or lock location. In the case of an ignition lock, the reduced visibility may make it more difficult for the driver to insert a key. This visibility problem can be further compounded for rectangular wave-cut key blades that lack the classic pointed key tip which provides some self-location aid to align the key with the ignition lock hole. Some vehicles have used interior lighting to illuminate the steering lock in an attempt to provide better visibility of the steering lock, however if a driver has to bend over to look around the steering wheel to locate the steering lock, often the driver's head may block the interior lighting defeating its purpose. Further, on some right-hand drive vehicles the driver may have to open the driver door to allow space for their head when bending over to look for the ignition lock.